Fantagraphics announced Thompson's death Wednesday, four months after he was diagnosed with lung cancer. He was 56.

Fantagraphics has been publishing since 1976, beginning with literary and comics, journalism and essays, and then comics, graphic novels, anthologies and translations of works from other languages. Many of its titles are some of the best known among readers and collectors of graphic novels and books, with works like "Love and Rockets" by Gilbert and Jaime Hernandez; Daniel Clowes' "Ghost World" and the "Acme Novelty Library."

Thompson was born in Denmark and moved to the U.S. when he was 21 in 1977. Soon after arriving, Thompson met Gary Groth and Michael Catron who founded Fantagraphics. He began contributing to "The Comics Journal" soon after.

"He was my partner and close friend for 36 years," Groth said in a statement.

Along with Groth, Thompson was one of the leaders in bringing adult themes and diverse characters into comics, along with stripping the focus on superheroes.

"It's a whole generation of guys who came along ... in the mid-1970s, they decided to see more and better comics, not just gutter media, lowest common denominator media it had become," said Tom Spurgeon, who worked with Thompson in the 1990s at "The Comics Journal" and now runs the website The Comics Reporter. "He thought comics could be anything — it's just words and pictures together, why not have stories with themes and ideas and represent people of different nationalities, genders, sexual orientation, race."

Thompson, however, appreciated the superhero comics, too, Spurgeon said. His fan letters were published by Marvel in the early 1970s, before he arrived in the United States. He also edited Fantagraphics' "Amazing Heroes," a bi-weekly magazine that focused on mainstream publishers like DC, Marvel as well as other houses like Comico and Eclipse, among others, in the 1980s.

"Kim loved the energy around the Journal and the whole idea of a magazine devoted to writing about comics, and asked if he could help," Groth said in a statement, recalling the days he worked out of an apartment.

"We needed all the help we could get, of course, so we gladly accepted his offer. He started to come over every day and was soon camping out on the floor. The three of us were living and breathing 'The Comics Journal' 24 hours a day."

Thompson's fluency in languages helped him translate several key editions of European titles into English, giving works by creators like Jacques Tardi, Ulli Lust and Guy Peelaert a wider audience for their creations.

Thompson is survived by his wife, Lynn Emmert, mother, father and his brother.

Jaime Hernandez, author of "Love and Rockets," tweeted: "While Gary's the in-your-face ballbuster, Kim was the quiet ballbuster. Both were needed to save comics. Good job, Kim. #rip"